Two major problems associated with wool are its tendencies to prickle (itch) and shrink. Improvements in softness and handle of wool can be achieved by addition of various chemical agents such as silicone softeners or by addition of proteolytic enzymes; however, the cost of these improvements may outweigh the moderate benefits achieved. Furthermore, changes in one property of wool can sometimes have an adverse effect on other properties. For example, protease treatments typically have adverse effects on strength and weight of wool material.
The most commonly used method to increase the shrink-resistance of wool is the IWS/CSIRO Chlorine Hercosett process, which involves acid chlorination followed by application of a polymer. This process imparts a high degree of shrink-resistance to wool, but adversely affects the handle of wool, damages wool fibers, and generates environmentally damaging waste.
Methods intended to maximize beneficial effects while minimizing damage generally attempt to confine degradative reactions to the fiber surface, thereby avoiding serious damage throughout the fiber. McPhee, Text. Research J., 1960, 30:358, describes treatment of fibers with potassium permanganate in a saturated salt solution, under which conditions fiber swelling is reduced. Degradative agents in organic solvents have also been used to modify fiber surfaces under non-swelling conditions. Leeder et al., Proc. 7.sup.th Int. Wool Text. Res. Conf., Tokyo, 1985, Vol. IV, 312, describes methods for treating wool under non-swelling conditions using a range of anhydrous alkalies in alcohol solvents. Such treatments provide wool with improved shrink-resistance and superior dyeing properties.
Various enzymatic methods have been used to treat wool. JP-A 51099196 describes a process to treat wool fabrics with alkaline proteases. WO 98/27264 describes a method for reducing the shrinkage of wool comprising contacting wool with an oxidase or a peroxidase solution under conditions suitable for reacting the enzyme with wool. U.S. Pat. No. 4,533,359 describes a process for descaling animal fiber which comprises surface-oxidizing the animal fiber with an oxidizing agent and subsequently treating the fiber with a proteolytic enzyme in a saturated or nearly saturated aqueous inorganic-salt solution. U.S. Pat. No. 5,529,928 describes a process for obtaining a wool with a soft woolly handle and shrink-resistant properties by using an initial treatment such as, e.g., a chemical oxidative step or treatment with a peroxidase, catalase, or lipase, followed by protease and heat treatments. EP 358386 A2 describes a method to treat wool which comprises a proteolytic treatment and one of or both an oxidative treatment (such as NaOCl) and a polymer treatment. EP 134267 describes a method for treating animal fibers with an oxidizing agent followed by a proteolytic enzyme in a salt-containing composition.
The environmental and performance deficiencies associated with current industrial processes for wool treatment substantiate the need for novel processes that provide further improvements relating to shrink-resistance or softness. Enzymatic methods for treating wool, used alone or in conjunction with an oxidative chemical step, have had minimal commercial success, which can be attributed to their relatively high cost and their tendency to damage wool by causing weight and strength losses. Thus, there is a need in the art for improved methods to treat wool, wool fibers, or animal hair material which impart improvements in softness, shrink-resistance, appearance, whiteness, dye uptake, and resistance to pilling, but cause less fiber damage than known treatments.